Attention is being given to the development of a micromachine or a nanomachine that mechanically moves according to the size of a molecule. This is because such micromachine or nanomachine is considered useful for, e.g., a molecule robot that lays out the wiring of a molecule computer or a medical robot that works a cure in the body.
For the fabrication of a micromachine and a nanomachine, development of a variety of technologies is required, including individual element devices (a sensor, an actuator and a miniature machine) to processes of assembling them (micromachining and nanomaching). In particular, the development of microactuators and nanoactuators (rotary motors), i.e., micromachine drive devices, is essential for self-regulating movement of machines, and the development of motor devices utilizing diverse precise handling technologies is being pursued. However, even microactuators made by processes to which precise handling technologies are applied are no smaller than about 100 μm. Further miniaturization of motor apparatuses is being required to install them in micromachines and nanomachines.
Thus, aside from construction of a motor by precise handling technology, utilization of a single molecule having rotary movement capability as a motor is proposed.
In general, a molecule capable of being a motor needs to satisfy two factors: having a power mechanism that converts outer energy into rotary movement, and achieving rotation in one direction. Low molecular organic compounds satisfying such conditions that are known include, for example, (3R,3′R)-(P,P)-trans-1,1′,2,2′,3,3′,4,4′-octahydro-3,3′-dimethyl-4,4′-bipheant hrydiene (Nature 401: 152-155, 1999) and Triptycyl(4)helicene (Nature 401: 150-152, 1999). The former has symmetry to the right and to the left of the carbon-carbon double bond, but has a twisted structure due to steric interlocking. Addition of suitable heat or light thereto makes it possible to rotate the molecule in one direction through four process steps. Also, one cycle is completed through two light reactions and a heat isomerization, with the movement proceeding in one direction only. In other words, this organic compound conducts rotary motion via heat isomerization and light reaction. Rotation via light reaction is very rapid (a level of picoseconds), but rotation via heat isomerization needs a few minutes, and so is unsuitable for actual use. Furthermore, the compound poses the problem that the driving force of rotation is extremely weak. On the other hand, the heat isomerization causes one-direction rotation of the molecule utilizing the chemical reactions of phosgene addition and the formation and cleavage of urethane bonding. However, this molecule is incapable of repeating rotation, a fatal defect for an actuator.
On the other hand, as a single molecule motor capable of being utilized in a micromachine, a nanomachine or the like, biomolecules are known that include a flagellum motor (Microbiol. 6: 1-18, 1967, Nature 245: 380-382, 1973), an ATP synthase (Nature 386: 299-302, 1997), a myosin motor (Biochem. Biophys. Res. Comm. 199: 1057-1063, 1994, Curr. Opin. Cell Biol. 7: 89-93, 1995), a microtubule-based motor (Cell 42: 39-50, 1985), a motor protein of nucleic acid synthase (Nature 409: 113-119, 2001, and the like.
Of these, an ATP synthase is a membrane protein present ubiquitous, at such locations as the inner membranes of mitochondria in eukaryotes, thylakoid membranes of chloroplasts, a prokaryote cell membrane, and the like, and synthesizes most ATP consumed in cells. An ATP synthase (F0F1,-ATP synthase) is a huge membrane protein complex with molecular weight up to about 500 thousand, and consists of an F0 portion present inside a membrane and an F1 portion present outside the membrane. The F0 portion is a passage for a proton (H+) to pass through the membrane, and the F1 portion is a catalyst portion that synthesizes and hydrolyzes ATP. The molecular weight of the F1 portion is about 380 thousand, for example, the subunit composition of the F1 portion in an ATP synthase derived from bacteria is α3β3δγ1ε1. α and β subunits both have a similar ATP binding portion, but catalyst activity is present in the β subunit. Both alternately align to form a ring and in the center of this α3β3 ring, a γ subunit is present. A δ subunit binds to the top of the α3β3 ring; an ε subunit that controls ATP hydrolysis activity binds to the γ subunit. On the other hand, the F0 portion has a molecular weight of about 100 thousands, and the amino acid composition contains in quantity glutamic acid and asparaginic acid, necessary for proton movement. The subunit composition is a1b2c9-12, “c” subunits are arranged like a ring (the “c” ring) in the membrane, and to the “c” ring are bound subunit “a” and two “b” subunits each having an arm protruding far outside the membrane. Hence, an F0F1-ATP synthase has an F1 portion and an F0 portion which are bound to each other at two sites: γε-“c” ring and δb2. A further characteristic is the fact that this F0F1,-ATP synthase molecule has two kinds of torque generating devices. One is an ATP driving type device present in the F1 portion and the other is a proton driving type device present in the F0 portion. That is, when the F0 portion takes a proton in the cell membrane, the “c” ring rotates clockwise; when the F0 portion discharges a proton to the outside of the cell membrane, the “c” ring rotates anticlockwise. On the other hand, during ATP synthesis, the F, portion rotates clockwise viewing the γ subunit from the F0 side, and the F1 portion rotates anticlockwise during ATP decomposition. By providing these two kinds of torque generating devices, the torque generated by ATP synthase is on the order of tens of piconewton·nm, and thus the synthase has a sufficient driving force for a molecule motor. Additionally, an ATP synthase acts in a water system and so it is most suitable as an actuator working in the body, and also can manipulate a protein, sugar, a lipid, or a nucleic acid in the body because it has sufficient power for moving actin.
The inventors of the present invention improved this F1F1-ATP synthase molecule, and have already invented and filed the invention of a modified F0F1-ATP synthase molecule capable of controlling over a wide rotation speed range and its utilization (Japanese Patent Application No. 2002-148232; filing date: May 22, 2002). In addition, recently, reported was a rotary motor molecule, which is made by incorporating a zinc binding site into an F1-ATP synthase molecule and which is capable of controlling the initiation and stop of the rotation by means of the zinc (Nature Materials 1: 173-177, 2002).
As described above, various rotary motor molecules are proposed as driving members of a micromachine, a nanomachine, and the like, and the molecules each have characteristics regarding type of rotation, the revolution number, torque, the method of controlling rotation, etc. Accordingly, for actual fabrication of a micromachine or a nanomachine, an appropriate molecule needs to be selected from a variety of candidate molecules depending on its application and machine construction. However, it cannot be said that the rotary motor molecules reported thus far can each be suitable for all the different applications and constructions of a micromachine and a nanomachine. For this reason, upon the development of a micromachine or a nanomachine or the like, each addition of one more to the lineup of rotary motor molecules is greatly desired.
Thus, this application is intended to provide a novel rotary motor molecule that is different in properties from the conventional rotary motor molecules.
In addition, the application also has another subject of providing an improved, novel rotary motor molecule which further smoothens the rotary motion and also adds a means for the molecule to transfer the rotary motion.